The present invention relates to thin film magnetic recording heads. In particular, the invention relates to an improved thin film magnetic head design which reduces undershoot or inter-symbol interference.
In a magnetic storage system, such as a computer disk drive, digital information is magnetically stored upon the surface of a magnetic medium such as a magnetic storage disk. The digital information is represented by selectively polarizing the magnetic field of consecutive areas across the surface of the rotating magnetic disk. When this information is read back from the storage disk, the magnetic polarization of the medium is sensed as an electrical output signal. The read and write operations are performed by a magnetic read/write head which is flying over the surface of the rotating disk.
The electrical output signal is representative of both the relative strength of the magnetization in the media, and the magnetic field pattern of the read head. It is highly desirable to provide the highest level of information storage density possible for a given magnetic storage system. Unfortunately, increased storage density leads to a lower signal-to-noise ratio for the sensed signal from a given disk. The readback signal comprises a series of superimposed symbols whose existence and location are used to represent digital information.
Signal recovery errors will result if the detection circuitry is confused in one of the following three ways:
1) Detecting a symbol that was not written; PA1 2) Rejecting a symbol that was written; PA1 3) Placing a written symbol in the wrong clock cell.
Cost effective detectors presently in use are confused by leading and trailing undershoots in the isolated readback pulse just as easily as they are confused by noise.
Therefore, the undershoots reduce the maximum recording density which may be achieved in a magnetic storage system. Undershoot occurs due to the discontinuities in the magnetic readback flux path characteristic of the infinite pole lengths of the thin film recording head. Rather than trying to compensate for the undershoots in the data signal using sophisticated electronic decoding methods, it would be highly desirable and a significant contribution to the art to provide a thin film magnetic head which minimizes the leading and trailing undershoots in the isolated readback pulse.